Causes and Fixes U0100 Code: Lost Communication with ECM/PCM

How to fix a U0100 engine code: Lost Communication with ECM/PCM
Test OBDII Port Video:    • Fixes OBDII Scan Tool Does Not Commun...  

A U0100 means that the vehicle CAN Bus can’t communicate with the engine control module (ECM), power-train control (PCM), module transmission control module (TCM), or other computer modules.
The CAN (Controller Area Network) is a protocol that allows the ECM, PCM, TCM and other modules to communicate with each other.
Diagnosing a U0100 can be difficult and time-consuming.

Possible Causes of the U0100 Code
Issues with Alternator Charging or Battery
Blown Fuse (Check OBDII Port Has Power)
Wiring Harness Open or Short
Wiring Harness Has Bad Ground
Faulty ECM TCM PCM

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